HX64142213 
RC 116  .  H34  Some  recent  advances 


RECAP 


KEADLEE 


SOME  RECENT  ADVANCES  IN  KNOWLEDGE 
..  AND  CONTROL  OF  MOSQUITOES 


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H34- 


Columbia  (Bntoergitp 
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College  of  ipfjpstctansi  ano  Hmrgeon* 


Htbrarp 


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in  2010  with  funding  from 

Open  Knowledge  Commons 


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SOME    RECENT   ADVANCES   IN   KNOWLEDGE    OF   THE   NATURAL 
HISTORY  AND  THE  CONTROL   OP  MOSQUITOES 


NEW    JERSEY 


AGRICULTURAL 


Ixgterlineiti   Stall® 


BULLETIN   306 


New  Brunswick,  N.  J. 


NEW  JERSEY  AGRICULTURAL  EXPERIMENT  STATIONS 

New   Brunswick,   N.  J. 

X    STATE    STATION      ESTABLISHED    1880. 
BOARD    OF    MANAGERS. 


His   Excellency   WALTER  E.    EDGE 
W.    H.  S.   DEMAREST,  D.    U, 
JACOB   G.    LIPMAN.    Ph.    D., 


Trenton,   Governor   of   the  State  of  New  Jersey. 

New  Brunswick,   President  of  the  State  Agricultural  College. 

Professor   of  Agriculture  of  the  State  Agricultural  College. 


FIRST     CONGRESSIONAL    DISTRICT. 

Ephraim   T.   Gill '■  Haddonfield. 

Wilhur  F.    Beckett Swedesboro. 

SECOND    CONGRESSIONAL    DISTRICT. 

Rhosha  Thompson Wrightstown. 

Charles  F.   Seabrook Bridgeton. 

THIRD    CONGRESSIONAL    DISTRICT. 

James  C.   Richdale Phalanx 

James  Neilson New  Brunswick. 

FOURTH    CONGRESSIONAL    DISTRICT. 

Josiah  T.   Allinson Yardville. 

John  Dawes,  Jr Lebanon. 

FIFTH    CONGRESSIONAL    DISTRICT. 

Daniel  B.   Wade Union. 

Theodore   F.   King Ledgewood. 

SIXTH    CONGRESSIONAL    DISTRICT. 

Nicodemus   Warne Broadway. 

Frederick   M.   Curtis Harrington   Park 

STAFF. 

JACOB    G.    LIPMAN,    Ph.    D., Director. 

IRVING    E.    QUACKENBOSS, Chief    Clerk, 

CARL  R.    WOODWARD,  B.  Sc Editor. 


SEVENTH    CONGRESSIONAL    DISTRICT. 

John  Holback Paterson. 

Henry  xMarelli Paterson. 

EIGHTH    CONGRESSIONAL    DISTRICT. 
Vacancy. 

James  McCarthy Jersey  City. 

NINTH    CONGRESSIONAL    DISTRICT. 

George  Smith East  Orange. 

William  Reid Orange. 

TENTH     CONGRESSIONAL     DISTRICT. 

George  E.  DeCamp Roseland. 

Harry  Backus Caldwell. 

ELEVENTH    CONGRESSIONAL    DISTRICT 

Herman  C.   Lange Hoboken. 

Richard  B.   Meany Weehawken. 

TWELFTH    CONGRESSIONAL    DISTRICT. 

Addison  T.  Hastings,  Jr Jersey  City. 

John  R.  Hartung Jersey  City. 


Secretary    and    Treasurer. 


CHARLES    S.    CATHCART,    M.    Sc,     Chemist. 
KALPH    L.    WILLIS,    B.    Sc,  Assistant   Chemist. 
FRANK    O.    FITTS,    B.    Sc,  Assistant    Chemist. 
D.    JAMES    KAY,    B.    Sc,    Assistant    Chemist. 
-ARCHIE    C.    WARK,      Laboratory    Assistant. 
W.    ANDREW    CRAY,   Sampler    and    Assistant. 
HERBERT    P.    ROOD,   Sampler    and    Assistant. 
ALVA    AGEE,    M.    Sc..' 

Chief    of    Extension     Department. 
JOHN    H.    HANKINSON.    A.    B.. 

State    Leader    of    Farm    Demonstration. 
VICTOR    G.    AUBRYL    B.    Sc. 

Extension    Specialist    in    Poultry    Husbandry. 
KOSCOE     W.     DE    BAUN.     B.     Sc. 

Extension    Specialist    in    Market   Gardening. 
JULIAN    F.    MILLER,    B.    Sc, 

Extension    Specialist    in    Fruit   Growing. 
HARRY   C.    HAINES, 

Asst.     Extension     Specialist  in  Fruit  Growing. 
J.    B.    R.    DICKEY.    B.    Sc,  Extension  Specialist 

in    Soil     Fertility,    and    Agronomy. 
ALLEN    G.    WALLER.    B.    Sc. 

Asst.    Extension    Specialist    in    Agronomy. 
JOHN    W.    BARTLETT.    B.    Sc. 

Extension    Specialist   in    Dairy    Husbandry. 
HOWARD  F.   HUBER.    B.    Sc, 

Specialist    in    Extension   Division. 
CHARLES  H.  NISSLEY.   B.   Sc. 

Specialist,  Extension  Division. 
A.    M.    HULBERT, 

State    Leader    in    Bovs'    Club    Work. 
M.    ANNA    HAUSER,    B.     Sc. 

Extension    Specialist    in    Home    Economies. 
CARRIE   M.    PIMM,    B.    Sc, 
Asst.  Extension  Specialist  in  Home  Economics. 
FANNIE    F.    COOPER.    B.    S. 

State    Leader    in    Girls'    Club    Work. 
HELEN  E.   MINCH, 

Assistant  in   Girls'   Club  Work. 
WILLIAM    J.    CARSON,    B.    S.    A., 

Dairy   Husbandman. 

2.  AGRICULTURAL    COLLEGE 


LLOYD    S.    RIFORD.    M.    Sc, 

.Assistant    Dairy    Husbandman. 
OHARI.KSS    VANNU1S    Associate  111  Farm  Crops. 
HARRY  C.  McLEAN,  M.  Sc, 

Chemist,     Soil     Research. 
FRANK    APP,    B.    Sc,     Agronomist. 
THOMAS    J.     HEADLEE,     Ph.   D..  Entomologist 
CHARLES    S.    BECKWITH,    B.    Sc. 

Assistant   Entomologist. 
FREDERICK    C.    MINKLER,    B.    Si    A., 

Animal    Husbandman. 
J.    MARSHALL    HUNTER.    B.    Sc, 

Assistant    Animal    Husbandman. 
JOHN    P.    MET.YAR.    M.    Sc,  Seed    Analyst. 
NEVADA     S.     EVANS,    A.    M., 

Assistant    Seed    Analyst. 
MAURICE    A.     BLAKE.    B.    Sc.    Horticulturist. 
CHARLES   H.    CONNORS.    B.    Sc. 

Assistant    in    Experimental    Horticulture. 
ARTHUR    J.    FARLEY,    B.    Sc, 

Specialist    in     Fruit     Studies. 
LYMAN    G.    SCHERMERHORN.    B.    Sc. 

Specialist  in  Vegetable  Studies. 
LOUIS  A.  RUZICKA.  Greenhouse  Assistant. 
W.  RAYMOND  STONE,  Orchard  Foreman. 
DAVID  SCHMIDT,  B.  Sc,  Field  Assistant. 
PAUL  J.  SASSI.  Field  Assistant. 
HERMAN    J.    LEVINE.    B.    Sc, 

Assistant    in    Vegetable    Gardening. 

HARRY   R.   LEWIS,   M.    Agr., 

Poultry    Husbandman. 
WILLARD    C.    THOMPSON,    B.    Sc. 

Assistant    in    Poultry    Research. 

ROY    F.    IRVIN,    B.    Sc. 

Specialist   in   Incubation   Studies. 
MORRIS    SIEOEL.    Poultry     Foreman. 
ELMER     H.     WENE. 

Poultry     Foreman. 


W.  H.  S. 


STATION      ESTABLISHED    1888. 
BOARD    OF    CONTROL 

The   Board    of   Trustees   of   Rucgers   College    in    New   Jersey. 
EXECUTIVE    COMMITTEE    OF    THE  BOARD. 

DEMAREST,   D.   D.,  President  of  Rutgers   College,    Chairman .  .New  Brunswick. 


HK^SJB^-..:'::::::::: ::::::::::::::::::::  ::$S  §=§: 

PHILIP    M.     BRETT 

DRURY    W.    COOPER 

WILLIAM    S.    MYERS 

STAFF. 

JACOB    G.    LIPMAN.    Ph.    D ■ £ir-e$t??i™i, 

HENRY  P.  SCHNEEWEISS,  A.  B Chief   LierK. 


New  Brunswick. 
.New  York  City 
.New  Y'ork  City 


BYRON  D.  HALSTED,  Sc.  D.,  Botanist. 
JOHN  W.  SHIVE,  Ph.  D.,  Plant  Physiologist. 
EARLE  J.  OWEN.  M.  Sc.  Assistant  in  Botany. 
MATHILDE  GROTH,  Laboratory  Aid. 
MF.T.VILLE  T.  COOK.  Ph.D.,  Plant  Pathologist. 
THOMAS  J.  HEADLEE. Ph.  D.,  Entomologist. 
ALVAH    PKTEKSON,  .Ph.  D.. 

Assistant  Entomologist. 


AUGUSTA    E.    MESKE, 

Stenographer    and    Clerk. 
JACOB    G.    LIPMAN,    Ph.    D., 

Soil    Chemist    and    Bacteriologist. 
AUGUSTINE    W.    BLAIR,    A.    M., 
Associate    Soil    Chemist. 
LOUTS    K.    WTLKINS,    B.    Sc, 

Field    and    Laboratory  Assistant. 


// 


3* 


CONTENTS 


PAGE 
DISTRIBUTION     5 

Migration 6 

Suggested  Method  of  Making  Mosquito  Collections     9 

Drainage     10 

Upland  Drainage   10 

Salt-Marsh  Drainage   10 

Ditching   10 

Diking  and  Tidegating  14 

Pumping 21 

Larvicides    24 

Sulfuric   Acid 24 

Chlorine    25 

Electrolysis     26 

Nitre  Cake 26 


(3) 


ILLUSTRATIONS 


PAGE 


Fig.  1. — Diagram  to  illustrate  the  method  of  determining 
mosquito  conditions  by  evening  collections  of  mos- 
quitoes on  the  wing 8 

Fig.  2. — Parallel  and  hole-connecting  schemes  of  ditching  .  .  12 

Fig.  3.— Eaton  ditcher   13 

Fig.  4. — Diagram  of  cross-section  of  a  dike 15 

Fig.  5. — Dike  in  process  of  construction 16 

Fig.  6. — Diagram  of  sluice  box  and  tide  gate 17 

Fig.  7. — Photograph  of  tide  gate  and  sluice 19 

Fig.  8. — Relative  level  of  water  on  the  protected  area  as 

compared  with  the  tide   20 

Fig.  9. — Diagram  of  Frank  Creek  area,  showing  ditching 

outlets  and  pumps   ...      22 

Fig.  10. — Twelve-inch  centrifugal  pump,  which  was  in- 
stalled to  drain  an  area  of  marsh  slightly  below 
sea  level   24 


(4) 


NEW   JERSEY 

Agricultural  Experiment  Stations 

bulletin  306 

OCTOBER  17,  1916 


SOME  RECENT  ADVANCES  IN  KNOWLEDGE  OF  THE 

NATURAL  HISTORY  AND  THE  CONTROL 

OF  MOSQUITOES 

By 

Thomas  J.  Headlee,  Ph.  D. 

Distribution 

Ever  since  the  publication  of  the  late  Dr.  John  B.  Smith's' 
report  on  the  mosquitoes  of  New  Jersey  we  have  known  that  tne 
brown  salt-marsh  mosquito  Aedes  cant  at  or  Coq.,  is  dominant  in 
early  spring  along  the  northern  two-thirds  of  the  state's  Atlantic 
coastline  and  that  it  gives  way  from  mid-summer,  or  in  some  cases 
late  summer,  on,  to  the  white-banded  salt-marsh  mosquito  (Aedes 
sollicitans  Wlk.).  More  recently  it  has  been  discovered  that  the 
former  apparently  predominates  in  the  southern  one-third  also, 
early  in  the  season,  and  that  it  is  practically  the  only  species  which 
breeds  on  the  northern  portion  of  the  Hackensack  Valley  salt  marsh. 
This  peculiarity  of  distribution  led  the  author  to  suspect  that 
salinity  played  a  determining  part  in  limiting  the  species  because 
the  only  factor  likely  to  exhibit  a  reasonably  constant  difference 
throughout  this  territory  and  throughout  the  season  was  salinity. 
This  year  (1915)  a  study  of  the  salinity  of  the  water  in  relation 
to  these  species  of  larva?  in  both  laboratory  and  salt  marsh  by 
Dr.  F.  E.  Chidester2  has  shown  that  highly  saline  water  (10  to  15 
per  cent)  is  favorable  to  the  growth  of  the  wrigglers  of  the  white- 
banded  salt-marsh  mosquito  and  injurious  (deadly  if  sufficiently 
high)  to  the  wrigglers  of  the  brown  salt-marsh  mosquito,  while  only 
slightly  salt  water  (6  to  8  per  cent)  is  favorable  to  the  latter  and 
injurious  to  the  former.  The  younger  the  larvse  the  more  acutely 
are  they  affected  by  the  degree  of  salinity.  Speaking  broadly,  we 
may  say  that  the  salinity  of  the  marsh,  especially  near  the  upland, 
is  lower  in  the  spring  than  during  any  other  part  of  the  mosquito 
season  and  concomitantly  the  brown  salt-marsh  mosquito  is  dom- 
inant. Later  in  the  season  as  the  salinity  of  the  water  increases 
the  white-banded  species  becomes  dominant  except  where  owing  1c 
a  constant  influx  of  fresh  water  the  salinity  is  kept  at  a  low  point 

lSmith,  John  B.,  Report  of  the  New  Jersey  State  Agricultural  Ex- 
periment Stations  upon  the  mosquitoes  occurring  within  the  State, 
their  Habits,  Life  History,  etc.  19  04. 

2Chidester,  F.  E.  The  influence  of  salinity  on  the  development  of  cer- 
tain species  of  mosquito  larvae  and  its  bearing  on  the  problem  of 
distribution  of  species.  N.  J.  Agr.  Exp.  Sta.  Bui.  299.  1916. 

(5) 


6  New  Jersey  Agricultural  Experiment  Stations 

Migration 

The  work  of  the  late  Dr.  Smith3  has  served  to  show  that  the 
brown  salt-marsh  mosquito  (A.  cantator)  and  the  white-banded 
salt-marsh  mosquito  (A.  sollicitans)  migrate  for  long  distances  from 
the  places  where  they  breed.  Neither,  the  cause  nor  the  occasion 
of  their  flight  seems  to  have  been  satisfactorily  explained.  Upon 
the  former  the  work  has  thrown  no  light  but  on  the  latter  some 
significant  observations  have  been  made.  Mr.  Eaton's4  observations 
in  Atlantic  County  serve  strongly  to  indicate  that  these  mosquitoes 
migrate  considerable  distances  only  with  the  wind,  and  with  it 
only  when  the  velocity  is  low — 10  miles  an  hour  or  less  with  an 
optimum  near  to  5 — and  the  relative  humidity  high.  The  author's 
own  observations  serve  to  confirm  these  conclusions.  This,  of  course, 
carries  with  it  the  idea  that  immense  numbers  of  mosquitoes  fly 
out  to  sea.  On  this  point  he  is  unable  to  testify  from  personal 
experience,  but  it  is  a  matter  of  common  knowledge  along  the 
coast  that  boats  at  sea  off  the  coast  occasionally  meet  tremendous 
swarms  of  mosquitoes. 

Early  in  the  work  of  the  county  unit  it  became  obvious  that 
the  source  of  the  mosquitoes  occurring  in  a  particular  county  must 
be  determined,  for  despite  utmost  efforts  to  control  local  breeding 
a  pest  of  mosquitoes  occasionally  appeared  in  parts  of  the  protected 
territory.  It  seemed  apparent  from  Dr.  Smith's  1904  report  that 
he  and  his  assistants  were  accustomed  to  trace  salt-marsh  broods 
from  place  of  breeding  to  distant  points  through  the  medium  of 
getting  data  from  widely  separated  observers  on  the  time  when  the 
mosquitoes  first  appeared  in  the  observers'  localities. 

It  occurred  to  the  author  that  the  tracing  might  be  done  very 
quickly  with  an  automobile  by  starting  in  uninfested  territory  close 
to  the  infested  area  and  collecting  at  regular  distances — say,  0.5 
of  a  mile  to  2  miles — until  the  mosquito  zone  had  been  traversed 
and  uninfested  country  found  on  the  other  side;  this  collection 
to  be  followed  by  a  similar  one  pursued  in  a  line  at  right  angles 
to  the  first. 

Two  assumptions  were,  of  course,  necessary  to  the  success  of 
this  plan,  one  of  which  is  that  the  mosquitoes  may  be  collected 
in  daylight  and  the  other  that  the  direction  of  greatest  density 
indicates  the  source  of  the  brood.  The  collections  were  made  in 
as  nearly  similar  places  as  possible,  especially  as  regards  the  char- 
acter of  the  growth,  and  the  relative  number  present  was  determined 
by  using  two  small  cyanide  tubes  and  catching  specimens  as  rapidly 
as  possible  for  a  definite  period  of  time,  then  reckoning  the  catch 
on  the  basis  of  so  many  per  minute. 

In  actual  practice  whenever  the  study  began  on  the  first  ap- 
pearance of  the  brood,  these,  assumptions  were  found  to  be  correct 
and  many  broods  have  in  this  manner  been  traced  to  their  places  of 
origin.  At  least  three  important  results  followed  the  discovery  and 
use  of  this  method,  the  first  was  the  finding  of  immense  breeding- 
areas  in  the  Hackensack  Valley  salt  marsh  in  sections  hitherto 

3Loc.  cit. 

4Eaton,  Harold  I.     Second  Ann.  Rpt.  Atlantic  Co.  Mosq.  Exter.  Com  , 
p.  39-43.  1914. 


Bulletin  306  7 

thought  to  be  free  of  breeding,  the  second  was  the  uncovering  of 
inefficiency  in  the  control  of  salt-marsh  breeding  on  certain  espec- 
ially dangerous  areas,  and  the  third  a  determined  and  apparently 
successful  effort  to  eliminate  the  breeding  places  thus  discovered. 

Scarcely  had  this  method  of  discovery  of  salt-marsh  breeding 
been  well  started  before  it  became  necessary  to  find  the  source  of 
a  brood  of  the  house  mosquito  (0.  pipiens)  which  in  spite  of  effort 
to  control  local  breeding  continued  to  infest  North  Elizabeth  in 
Union  County.  It  was  quickly  found  that  no  progress  could  be 
made  by  day  collections  and  that  a  difference  in  the  hour  when 
the  collections  were  made  gave  such  a  difference  in  the  number 
caught  that  determination  of  density  by  serial  collections  covering 
several  hours  was  impracticable.  Accordingly,  a  sufficiently  large 
number  of  inspectors  were  furnished  by  Union  and  Essex  Counties 
to  cover  a  line  extending  through  North  Elizabeth  to  and  through 
South  Newark  to  the  sewage-charged  salt  marshes,  each  man  col- 
lecting for  20  minutes  at  three  stations,  one-quarter  of  a  mile  apart 
from  each  other,  between  8.00  p.  m.  and  9.30  p.  m.  The  following 
evening  in  the  same  manner  a  line  from  the  marshes  running  at 
right  angles  to  the  first  was  collected.  In  this  instance  the  weather 
of  the  two  evenings  was  sufficiently  similar  to  render  the  results 
comparable  but  generally  it  would  be  better  to  have  enough  in- 
spectors to  collect  both  lines  at  the  same  time. 

A  careful  study  of. the  collections  showed  a  zone  of  house  mos- 
quitoes extending  from  North  Elizabeth  to  the  Ebling  section  of 
the  Essex  County  salt  marsh,  a  distance  of  at  least  2.5  miles,  with 
practically  steadily  increasing  density  as  the  marsh  edge  was  ap- 
proached. 

Examinations  of  the  marsh,  which  was  heavily  charged  with 
sewage,  showed  enormous  numbers  of  C.  salanarius  and  G.  pipiens 
with  small  numbers  of  A.  sollicitans  and  A.  cantator  in  larval  and 
pupal  stages.  The  question  has  been  raised  as  whether  supposed 
house  mosquitoes  were  not  really  salanarius.  Undoubtedly,  both 
C.  pipiens  and  C.  salanarius  were  component  portions  of  the  zone, 
but  the  smaller  portion  seemed  to  consist  of  the  smaller,  darker 
lankier  form  which  was  thought  to  be  the  latter.  It  seemed  only 
fair  to  conclude  that  while  C.  salanarius  played  a  part  in  forming 
this  mosquito  zone,  C.  pipiens  was  clearly  shown  in  this  case  to 
migrate  a  distance  of  2.5  miles  from  the  place  of  breeding. 

Later  the  president  of  the  Essex  County  Mosquito  Extermination 
Commission,  Dr.  Ralph  H.  Hunt,  and  the  chief  inspector  of  that 
organization,  Mr.  John  "W.  Dobbins,  demonstrated  in  a  similar 
manner  a  zone  of  the  house  mosquito  extending  from  the  Prank 
Creek  section  of  the  Kearny  marsh  to  the  western  edge  of  Branch 
Brook  Park  in  Newark,  a  distance  of  1.75  miles. 

It  is  interesting  in  this  connection  to  note  that  the  city  of 
New  Haven,  Conn.,  was  for  three  years  troubled  during  the  latter 
part  of  the  season  with  C.  pipiens  which  bred  in  the  dye-charged 
waters  of  "West  River.5 

These  facts  must  not  be  taken  to  indicate  that  the  house  mos- 
quito normally  migrates  such  distances.  As  a  matter  of  fact, 
much  study  of  this  species  on  the  wing  indicates  that  save  when 

oBritton,  W.  E.,  First  Ann.  Rpt.  N.  J.  Mos.  Exter.  Assoc,  p.  71. 


8  New  Jersey  Agricultural  Experiment  Stations 

bred  in  enormous  numbers  over  many  acres  of  sewage-charged  wat- 
er, its  distribution  is  "pocketed",  by  which  we  mean  that  areas  of 
great  density  are  small  and  isolated  from  each  other,  showing 
clearly  that  slight,  if  any,  migration  has  taken  place. 

The  discovery  of  this  characteristic  "pocketed"  distribution  of 
the  house  mosquito  led  the  writer  to  wonder  whether  a  careful 
charting  of  the  mosquitoes  on  the  wing  twice  each  week  would  not 


SALT    MARSH  '<     ','$'///, 

//  /  ' 


/ ' 


Fig.  1. — A  diagram  to  illustrate  the  method  of  determining  mosquito 
conditions  by  evening  collections  of  mosquitoes  on  the  wing.  The  area 
inclosed  in  the  solid  black  line  is  protected. 

*  =  Collection  stations. 

Numerals  =  number  of  mosquitoes  caught  at  each  station. 

AC  =  the  brown  salt-marsh  mosquito  (Aedes  cantator  Coq.,). 

AS  =  the  white-marked  salt-marsh  mosquito   (Aedes  sollicitans  Wlk.). 

A  sub.  =  the  brown  woods  mosquito  (Aedes  subcantans  Felt). 

A  syl.  =  the  fresh-water  swamp  mosquito  (Aedes  sylvestris  Theob.). 

CP  =  the  house  mosquito  (Culex  pipiens  Linn.).  Let  us  analyze  this 
diagram  and  see  what  it  means  for  each  species.  The  brown  salt-marsh 
mosquito  shows  heavily  along  the  eastern  border  and  decreases  regularly 
to  the  west  and  northwest.  Evidently  a  brood  had  invaded  the  area  from 
the  eastern  border.  Likewise  a  heavy  infestation  of  the  white-marked  salt- 
marsh  mosquito  appears  along  the  southern  border  and  decreases  regularly 
to  the  northward.  Evidently  there  has  been  an  invasion  of  this  species  from 
the  southward.  The  distribution  of  the  house  mosquito  is  irregular,  clearly 
indicating  that  overlooked  local  breeding  is  responsible.  The  occurrence 
of  10  brown  woods  mosquitoes  at  one  collection  station  indicates  the 
existence  of  local  breeding.  The  occurrence  of  1  swamp  mosquito  is 
too  slight  to  be  significant. 


Bulletin  306  9 

lead  to  the  discovery  of  these  pockets  in  their  incipiency,  and  in 
time  to  prevent  the  emergence  of  a  number  of  mosquitoes  sufficient 
to  give  the  householders  trouble.  While  temporarily  in  charge  of 
the  mosquito  control  work  in  Passaic  County  during  the  late  sum- 
mer of  1914,  opportunity  to  test  the  idea  arose.  The  semi-weekly 
collections  were  promptly  charted  and  the  pockets  of  C.  pipiens 
thus  indicated  were  promptly  investigated  for  breeding.  In  every 
case,  as  he  remembers  it,  some  special  breeding  place  hitherto  over- 
looked was  found  and  abolished,  with  the  result  that  the  concen- 
tration of  the  house  mosquito  at  that  point  promptly  disappeared. 

During  August  of  1915  the  distribution  of  the  swamp  mos- 
quito (Aecles  sylvestris  Theob.)  exhibited  unusual  features.  Stand- 
ing pools  ahnost  everywhere  in  clay  land  sections  of  the  state 
were  found  to  contain  larvae  of  this  species  and  for  a  time  it  was 
the  dominant  form.  It  will  be  interesting  to  note  the  effect  of  the 
tremendous  egg-laying  of  late  last  summer  on  the  early  spring 
emergence  of  this  species. 

Suggested  Method  of  Making  Mosquito  Collections 

There  is  no  occasion  to  begin  making  evening  collections  until 
the  breeding  conditions  indicate  that  mosquitoes  are  beginning  to 
get  on  the  wing  or  some  adults  are  discovered  incidentally.  In  the 
spring  when  we  have  the  salt-marsh,  the  woodland-pool,  and  the 
fresh-water  swamp  species  to  deal  with,  daylight  collections  will  be 
satisfactory,  provided  they  are  made  in  the  same  manner,  at  the 
same  time  and  in  similar  (preferably  weedy  or  shrubby)  places. 
When,  however,  as  from  early  summer  the  house  mosquitoes  must 
be  taken  into  consideration,  the  time  of  collection  should  be  be- 
tween 7.30  p.  m.  and  9  p.  m.  Each  collector  should  spend  at  least 
15  minutes  in  a  place  and  one  man  may  take  care  of  two  or  even 
three  places. 

If  the  territory  be  large  and  the  number  of  collectors  small, 
one  evening  each  week  should  be  given  to  the  county-wide  collec- 
tion and  various  limited  portions  of  the  territory  should  be  at- 
tended to  on  the  other  evenings. 

The  number  representing  each  species  at  each  station  should  be 
determined  on  the  following  morning  and  the  results  set  down 
upon  a  map  of  the  area.  If  here  and  there  over  the  map  small 
isolated  areas  where  mosquitoes  are  much  thicker  than  elsewhere 
are  found,  these  areas  should  without  delay  be  most  carefully 
searched  for  over-looked  breeding.  If  areas  of  considerable  size 
are  found  on  the  border  or  of  large  size  well  within  the  confines 
of  the  area,  they  should  at  once  be  further  studied.  If  the  species 
concerned  belongs  to  the  salt-marsh  or  fresh-water  swamp  or  wood- 
land-pool, daylight  collections  will  serve  to  get  at  the  facts,  but 
if  the  house  forms  are  to  blame  the  examinations  will  have  to  be 
made  in  the  evening.  In  either  case,  two  lines  of  collection  should 
be  made — one  running  through  the  dense  zone  in  one  direction  and 
the  other  at  right  angles.  The  direction  in  which  the  number  of 
mosquitoes  caught  grows  larger  is  the  source  of  the  brood  and  if 
the  tracing  is  done  promptly  the  larva?  or  pupa?,  or  pupal  shells 
will  be  found  where  the  brood  in  question  matured.  If  not 
promptly  traced  the  location  of  the  source  of  brood  may  be  found 
to  be  impossible. 

It  is  thought  that  by  use  of  these  methods  of  collection  the 


10  New  Jersey  Agricultural  Experiment  Stations 

density  of  the  mosquito  fauna  may  be  expressed  in  terms  of  so 
many  mosquitoes  a  minute  or  other  period  of  time,  and  that  the 
number  per  minute,  quantities  above  which  mean  trouble  to  the 
householder  and  below  which  mean  freedom  from  trouble,  will  soon 
be  determined  for  each  of  the  species  concerned.  It  is  thought  that 
experience  will  soon  define  the  increase  in  number,  which  means 
that  the  fresh-water  species,  especially  the  house  mosquito,  is  breed- 
ing unchecked  and  that  more  careful  examination  must  be  made. 
It  is  further  thought  that  this  increase  may  be  detected  early 
enough  to  find  the  breeding  and  to  eliminate  it  before  the  density 
of  the  fresh-water  mosquito  fauna  becomes  sufficient  to  trouble  the 
householder.  It  is  thought  that  the  practice  of  these  methods  will 
enable  the  exterminator  to  run  down  accurately  the  breeding  places 
from  which  the  invasion  of  migrational  mosquitoes  come  and  thus 
to  take  the  first  necessary  step^tow-ard  their  elimination. 

)rainage 
Up  to  1912  very  little  drainage  for  mosquito  control  purposes 
had  been  placed  on  the  upland  and  that  on  the  salt  marsh  consisted 
of  the  10x30-inch  trenching  with  natural  or  artificial  outlets  as 
the  case  demanded,  of  filling  the  salt  holes  with  sods  taken  from 
the  ditches,  of  trenching  to  a  central  hole,  or  sump,  and  of  cutting 
systems  of  parallel  ditches  connected  with  each  other  but  without 
outlet. 

Upland  Drainage 

Beginning  in  1912  the  county  mosquito  commissions  have 
cleaned  sluggish  brooks,  drained  stagnant  pools  and  swamps,  stock- 
ed others  with  fish,  and  filled  cisterns,  cesspools  and  lot  pools. 

In  the  operation  of  cleaning  brooks  the  bottoms  have  been 
regraded  so  as  to  permit  a  regular  flow  of  the  water,  the  sides  have 
been  cut  down  in  such  a  fashion  as  to  make  them  perpendicular 
and  to  render  it  difficult  for  grass  to  obtain  a  foothold.  In  the 
treatment  of  pools  and  swamps  the  effort  has  been  to  remove  the 
water.  Usually  open  ditches  cut  with  ordinary  picks  and  spades 
have  been  used,  but  in  some  cases  excellent  tile  drains  have  been 
installed. 

It  has  been  necessary  to  repair  work  on  cleaned  brooks  and 
open  ditches  each  year  for  the  frost  and  high  water  cause  the 
banks  to  cave  and  the  grade  to  lose  its  evenness. 

It  can  not  be  said  that  ditching  on  the  upland  has  exhibited 
any  marked  advance  in  methods. 

Salt-Marsh  Drainage 
Ditching 

On  the  salt-marsh  however,  it  has  become  plain  during  the 
last  three  years  that  no  salt  marsh  is  so  well  drained  that  it  will 
at  all  times  be  free  from  mosquito  breeding.  There  are  times  when, 
owing  to  high  tides,  continued  rain,  and  cloudy  weather  (during 
which  the  rate  of  evaporation  is  greatly  lowered),  the  water  de- 
rived either  from  high  tide  or  heavy  rainfall  or  from  both  fails 
to  be  drawn  off  in  time  to  prevent  the  maturing  of  the  last  remnant 
of  the  brood.  Moreover,  it  may  be  said  that  the  ditch  mouths 
become  plugged  with  sand  or  seaweed  through  the  action  of  the 
waves  and  that  by  one  means  or  another  the  ditches  farther  up  in 
their  courses  become  plugged  with  pieces  of  sod,  accumulations  of 
hay,  and  other  rubbish. 


Bulletin  306  11 

It  can  be  said,  however,  that  during  the  past  three  years  no 
case  has  come  to  the  author's  knowledge  in  which  the  10x30-inch 
trenching  of  the  ordinary  high-lying  salt  marsh  has  failed  to  elim- 
inate all  but  a  small  percentage  of  the  brood  which  started. 

The  apparent  inability  of  the  ditching  to  afford  complete  con- 
trol of  breeding  has  demonstrated  the  maintenance  of  a  patrol  of 
the  drained  salt  marshes  throughout  the  mosquito  breeding  season, 
as  one  of  the  measures  necessary  to  successful  mosquito  control 
work. 

The  greatest  differences  of  opinion  relative  to  the  amount  of 
trenching  necessary  to  free  an  acre  of  breeding  salt  marsh  from 
danger  have  existed,  and  to  a  considerable  extent  still  exist.  An 
attempt  to  discover  the  cause  for  this  difference  quickly  reveals 
that  each  opinion  is  based  on  the  particular  area  or  areas  of  salt 
marsh  with  which  the  persons  expressing  them  have  had  to  deal. 

Some  marshes,  owing  to  a  larger  percentage  of  the  area  being 
tilled  with  holes  and  depressions  in  which  the  high  tide  or  rain 
water  is  retained,  require  more  extensive  drainage  than  others. 
Furthermore,  some  marshes  are  protected  from  the  tide  by  dikes  and 
the  natural  drainage  Avater  is  removed  by  tide  sluices  or  even  by 
pumps,  and  require  on  that  account  less  trenching  than  would 
otherwise  be  the  case.  Other  marshes  are  very  wide  and  very 
poorly  supplied  with  natural  water-ways  into  which  the  primary 
trenching  may  be  opened,  and  require  on  that  account  a  larger 
amount  of  drainage,  the  extra  amount  being  necessary  in  cutting 
outlets  for  the  primary  system. 

The  estimated  requirements  range  from  90  to  600  linear  feet 
of  10  x  30-inch  ditching,  or  its  equivalent,  per  acre.  As  a  matter 
of  fact,  only  rarely  is  the  former  figure  practicable  and  then  under 
especially  favorable  conditions,  and  never  on  the  New  Jersey  salt 
marshes  has  the  latter  figure  been  reached.  It  seems  probable  that 
between  200  and  300  feet  is  the  real  average.  To  this  must  be 
added  an  amount  of  hole  filling  and  shallow  spurring  which  will 
add  about  10  per  cent  to  the  acre  cost.  Fortunately,  large  portions 
of  the  salt  marsh,  particularly  in  the  southern  part  of  the  state 
are  so  low-lying  and  open  to  the  tide  as  to  be  swept  by  every 
tide  which  is  a  little  higher  than  the  ordinary,  and  are  on  that 
account  so  free  from  breeding  as.  to  require  no  drainage.  In  a 
given  area  which  includes  a  considerable  amount  of  this  kind  of 
land,  the  required  number  of  feet  of  drainage  per  acre  will  be 
materially  reduced. 

The  plan  of  trenching  has  not  undergone  marked  changes.  By 
1912  two  general  plans  were  in  use — the  first  of  which  might  be 
called  the  parallel  system,  and  the  second,  the  pool-connecting 
system.  The  former  was  the  one  generally  in  use  while  the  latter 
was  thought  to  be  adapted  to  particular  conditions.  In  the  parallel 
ditching  scheme  the  territory  to  be  drained  was  divided  into  dis- 
tricts on  the  basis  of  the  possible  outlet  and  each  block  of  territory 
crossed  by  parallel  ditches,  lying  sufficiently  close  to  remove  the 
surface  water.  Holes  and  depressions  were  spurred  into  these 
parallel  ditches  or  filled  with  sod  or  other  material.  In  the  hole- 
connecting  scheme  ditches  were  run  from  one  hole  to  another  and 
finally  into  one  or  more  outlets.     It  was  held  that  such  a  plan 


12 


New  Jersey  Agricultural  Experiment  Stations 


«,<.»  mn«+   practicable  where  the  marshes  were   very   full   of   salt 
rKl  of  the  last  three  years  has  clearly  pomted 
out  the  superiority  of  the  parallel  ditching  and  the  hole-connecting 
plan  has  been  practically  abandoned. 


Fig.  2.— Parallel   (A)   and  hole-connecting   (B)    schemes  of  ditching. 

Early  in  the  salt-marsh  trenching  it  was  recognized  that  the 
type  of  outlet  was  of  supreme  importance  and  recent  experience 
has  served  to  confirm  this  notion.     The  greater  the  tide  drop  and 


Bulletin  306 


13 


the  shorter  the  ditch  the  greater  is  its  efficiency  and  its  ability  to 
keep  clean.  Every  ditch  should  have  a  strong  tidal  outlet  and  no 
ditch  depending  on  a  single  outlet  should  be  over  one-quarter  of  a 
mile  long. 

The  machinery  used  in  cutting  ditches  has  undergone  some 
important  changes.  The  hand  tools  have  made  little  if  any  ad- 
vance. The  Manahan  and  the  Skinner  types  of  spades  are  still 
the  prevalent  tools  and  are  so  covered  with  patents  that  the  trench- 
ing of  the  marsh  by  anyone  not  possessing  the  right  to  use  these 


B 


C 
Fig.  3.— Eaton  ditcher.     (Photos  by  Atlantic  Co.  Mos.  Exter.  Com).     (A) 
Near  and  front  view  of  power  plant  with  plow  in  distance;    (B)    Near  and 
rear   view   of   the   plow   showing   the   ditch   and   way  the   sods   are   disposed 
of;    (C)   A  ditch  cut  by  the  Eaton  ditcher. 

tools  is  both  difficult  and  expensive.  Recently,  Mr.  Harold  I. 
Eaton  has  invented  a  practicable  sort  of  hand  spade  but  as  a 
patent  will  be  placed  upon  it  the  general  public  does  not  seem 
to  be  in  a  way  to  benefit  by  it  materially. 


14  New  Jersey  Agricultural  Experiment  Stations 

A  power  machine  has  been  invented  by  Mr.  Eaton  which 
unquestionably  trenches  the  marsh  with  such  ease  and  speed  as 
to  make  a  notable  reduction  in  the  cost  of  ditching.  Essentially 
the  machine  consists  of  a  gasoline  power  plant  placed  on  a  pair 
of  12-foot  long,  12-inch  wide  and  2-inch  thick  planks  that  are 
set  within  5  feet  of  each  other  and  strongly  bound  together 
with  crossties.  The  front  and  rear  ends  of  the  machine 
each  bear  a  revolving  drum,  upon  which  a  500-foot  %-inch  steel 
cable  is  wound.  When  the  power  plant  must  be  moved  forward  or 
away  in  another  direction  the  anchor  to  which  this  front  cable  is 
bound  is  carried  out  in  the  desired  direction  and  thrown  into  the 
sod.  The  power  is  then  applied  to  the  drum  and  the  plant  is 
drawn  up  to  the  anchor. 

The  plow  or  trencher  consists  of  two  12-foot  long,  10-inch 
wide  and  2-inch  thick  planks  set  parallel  and  10  inches  apart. 
Suspended  between  these  planks  are  two  cutters.  The  point  of  the 
forward  one  is  15  inches  below  the  under  sides  of  the  planks  and 
the  point  of  the  second  30  inches  below.  As  the  machine  is  pulled 
forward  each  cutter  shears  out  and  brings  up  a  piece  of  sod  10 
inches  wide  and  15  inches  thick  which  it  deposits  as  a  long  ribbon 
on  one  side  of  the  ditch.  This  plow  is  attached  to  the  power 
plant  by  a  500-foot  steel  rope  which  is  wound  up  on  the  rear  drum, 
while  the  power  plant  is  standing  anchored  ahead. 

With  a  machine  of  this  sort,  which  can  be  had  for  $1750, 
and  5  men  it  is  possible  to  cut  3000  feet  of  trenching  a  day  and 
in  some  cases  more. 

Competition  and  the  invention  of  this  machine  have  cut  the 
cost  of  ditching  from  2]/2  cents  a  linear  foot  in  1912  to  less  than 
V/2  cents,  and  are  bound  to  bring  it  lower  yet.  The  operating  and 
up-keep  cost  of  ditching  with  this  machine,  as  shown  by  cutting 
hundreds  of  thousands  of  feet  in  the  past  two  years,  does  not 
exceed  one  cent  a  linear  foot. 

Diking  and  Tide-gating 

During  the  last  three  years  it  has  become  evident  that  while 
the  10  x  30-inch  trenching  serves  Avell  for  the  ordinary  type  of  salt 
marsh,  it  is  wholly  inadequate  to  protect  marshes  that  are  badly 
shut-in  and  low  lying.  This  was  well  illustrated  on  the  Essex 
County  marsh,  where  in  1914  in  spite  of  more  than  one  million 
feet  of  trenching  on  le^s  than  4000  acres,  an  unusual  combination 
of  continued  high  tide,  heavy  rainfall,  and  cloudy  weather  per- 
mitted the  emergence  of  a  tremendous  brood. 

To  protect  areas  of  this  type,  diking  and  tidegating  were 
undertaken.  The  Essex  County  commission  was  the  first  to  try 
this  method  of  preventing  mosquito  breeding.  The  idea  seemed  to 
this  organization  to  be  so  practicable  that  it  employed  Mr.  James 
E.  Brooks  of  Glen  Ridge  as  a  consulting  engineer  and  instructed 
him  to  prepare  plans.  Mr.  Brooks  examined  the  method  of  diking 
employed  in  the  Hackensack  Valley  and  along  the  coast  of  Dela- 
ware Bay  for  agricultural  purposes,  and  finally  devised  a  type  of 
dike  and  sluice  gate  that  have  had  two  years  of  trial,  and  during 
that  period  have  proven  satisfactory. 

Before  Mr.  Brooks  was  employed  and  later  while  he  was  pre- 


Bulletin  306 


15 


paring  his  plans,  Mr.  John  Dobbins  of  Newark,  the  chief  inspector 
of  the  Essex  County  commission,  enclosed  a  limited  area  of  bad 
breeding  sewage-charged  salt  marsh  with  a  low  mud  dike  in  which 
the  simplest  type  of  sluice  gates  was  set.  The  effectiveness  of  this 
preliminary  work  in  drying  out  the  previously  inaccessible  marsh 
was  such  as  to  justify  the  undertaking  of  more  extensive  work. 


Fig.   4. 


-Diagram   of   a  cross-section   of   a   dike. 
James  E.  Brooks.) 


(Prepared      by      Mi 


AVhen  Mr.  Brooks'  plans  were  ready  they  called  for  a  strong 
sod  dike  with  a  mud  core  and  for  substantial  permanent  sluice 
gates.  For  the  benefit  of  persons  who  may  have  to  meet  similar 
problems  necessary  space  will  be  taken  to  explain  the  nature  of 
this  dike  and  of  the  sluice  gates. 

The  height  of  the  dike  was  made  to  depend  upon  the  height 
of  the  tide  it  was  expected  to  keep  out.  In  this  case  the  dike 
was  built  to  an  elevation  of  7  feet  above  mean  low  tide  which  was 
one-half  of  a  foot  higher  than  the  previously  recorded  highest  tide 
for  the  season  of  1914.  The  intention  was  to  build  it  high  enough 
to  keep  out  all  but  the  very  highest  of  high  tides,  the  theory  being 
that  these  extraordinary  high  tides  come  so  rarely,  and  at  such 
times  of  the  year  that  fencing  them  out  is  unnecessary. 

The  dikes  as  they  were  built  stood  3  feet  above  the  meadow 
surface,  were  2  feet  wide  at  the  top  and  6  feet  wide  at  the  bottom. 
Anticipating  a  shrinkage  of  about  25  per  cent,  the  crest  was  made 
about  1  foot  higher  than  the  elevation  called  for. 

When  the  construction  of  the  dike  began,  a  trench  10  inches 
wide  by  20  inches  deep  was  cut  along  the  line  to  be  occupied  by 
the  structure,  and  the  sods  taken  out  utilized  in  making  the  dike. 
A  row  of  sods  composed  of  pieces  approximately  10  inches  wide. 
12  inches  high  and  26  inches  long  was  laid  on  each  side  of  this 
trench  with  the  grassy  ends, out  enclosing  a  space  20  inches  wide. 
Mud  was  then  tamped  into  the  trench  until  its  surface  was  flush 
with  the  upper  surface  of  the  sod  layer.  Then  another  layer  of 
sod  composed  of  pieces  10  inches  wide  by  12  inches  high  by  21 
inches  long  was  placed  on  top  of  each  of  the  two  other  layers. 
Again  the  grassy  ends  were  out  but  the  ends  of  the  upper  layer 
were  6  inches  nearer  the  dike  center  than  were  the  ends  of  the 
lower  layer.  The  central  cavity  thus  formed  was  tamped  full  of 
mud.  Then  a  third  layer  of  sod  was  placed  on  the  second  in  a 
similar  fashion  with  a  similar  approach  to  the  center.  The  space 
formed  between  the  two  parts  of  the  layers  was  tamped  full  of 
mud.     In  some  cases  the  dike  thus  constructed  was  covered  with  a 


16  New  Jersey  Agricultural  Experiment  Stations 


Fig.  5. — Dike  in  process  of  construction.  A.  Cutting  the  prelimin- 
ary trench;  B.  Tamping  in  the  mud  core;  C.  Gang  at  work  on  dike 
construction;  D.  Completed  dike  as  it  looked  during  the  following 
summer.      (Photos  by  Union  Co.  Mos.  Exter.  Com.) 


Bulletin  306 


17 


layer  of  sod  while  in  other  cases  the  crest  was  simply  rounded 
up  with  mud. 

The  sod  and  the  mud  for  making  the  dike  came  from  the  pre- 
liminary trench  and  from  a  supply  trench  which  was  dug  inside  the 
protected  area  about  8  feet  from  the  base  of  the  dike.  In  some 
eases  a  supply  trench  was  dug  on  each  side  of  the  dike.  In  every 
case  the  supply  trench  was  of  uniform  width,  did  not  exceed  3 
feet  in  depth  and  was  properly  connected  with  adecpiate  outlets. 

During  the  summer  of  1915  the  grass  in  the  sods  grew  vig- 
orously and  transformed  the  dike  into  a  wall  of  green.  The  sods 
used  in  capping  the  dike  dried  out  and  separated  until  they  looked 


i.M..aL 


Fig.    6.- 


-Diagram   of   sluice  box   and   tide 
James  E.  Brooks.) 


rate.      ( Prepared      by      Mr. 


like  the  battlements  on  a  wall,  and  the  layer  became  useless  as  a 
means  of  keeping  water  out.  The  mud  cap  settled  down  and  form- 
ed a  continuous  solid  cap  serving  much  better  the  purpose  for 
which  it  was  intended  than  did  the  sod  layer. 

Some  dikes  have  been  constructed  entirely  with  mud  but  al- 
ways in  places  where  sod  was  not  available.  In  such  instances  the 
mud  has  been  scooped  from  a  trench  back  of  the  dike  (forming 
a  ditch  paralleling  the  work  and  giving  useful  drainage),  and 
piled  up  until  a  dike  of  requisite  height  with  due  allowance  for 
shrinkage  had  been  built,  which  was  2  feet  wide  at  the  top  and  as 
broad  at  the  base  as  was  demanded  by  the  normal  angle  of  repose. 
This  type  of  dike  does  not  withstand  the  weather  or  the  water  as 
well  as  the  sod  type  but  is  efficient  if  carefully  looked  after. 

At  points  where  streams  or  larger  ditches  cross  the  dikes 
sluice  boxes  and  tide  gates  were  introduced.  The  largest  sluice 
box  used  measured  inside  3  feet  high,  6  feet  wide  and  24  feet  long. 
It  was  made  of  2-inch  lumber  nailed  to  outside  ribs  at  distances 
of  18  inches  apart.  The  box  was  set  on  2  rows  of  2-inch  sheet 
piling  and  then  covered  with  soil.     A  large  heavy  wooden  door 


18  New  Jersey  Agricultural  Experiment  Stations 

was  suspended  over  the  down-stream  end  of  the  box  to  serve  as  a 
tide  gate.  The  following  specifications  have  been  used  in  the  con- 
struction of  sluices  employed  as  an  outlet  for  a  large  creek  which 
at  the  point  where  the  gates  were  introduced  was  75  to  80  feet  wide. 

1.  All  sluices  shall  have  an  inside  measurement  of  6  x  3  feet 
and  shall  be  built  of  3-inch  tongued  and  grooved  long-leaf-pine, 
free  from  knots  or  serious  blemish;  they  shall  not  be  shorter  than 
15^2  feet  and  shall  extend  from  the  outside  of  the  dike  facing 
back  under  the  dike.  These  boxes  shall  be  stiffened  with  4  x  5-inch 
ribs  bolted  at  each  corner  with  a  ^2 -inch  bolt  properly  washered 
and  drawn  up  with  a  satisfactory  nut.  These  ribs  shall  be  placed 
around  the  outside  of  the  box  fitting  it  closely  at  distances  of  18 
inches  apart.  The  first  and  last  shall  be  made  flush  with  the  ends 
of  the  box.  The  planking  shall  be  firmly  spiked  to  these  ribs  with 
6-inch  galvanized  spikes.  The  top  of  the  box  shall  be  covered 
with  2-inch  long-leaf -pine  spiked  on  the  top  of  the  ribs. 

2.  The  dike  shall  be  faced  on  the  river  side  with  plank  piling 
for  120  feet  at  the  mouth  of  Kingsland  Creek.  This  facing  shall 
consist  of  3-inch  long-leaf -pine  planking,  free  from  knots  and  ser- 
ious blemish,  not  less  than  1-1  feet  long  driven  in  until  the  top  shall 
be  one  foot  below  the  level  given  for  the  top  of  the  dike.  If  the 
tops  of  the. piles  are  splintered,  split  or  broomed  by  driving,  they 
shall  be  cut  off  below  the  lowest  point  of  injury.  In  any  case  the 
cut  of  ends  shall  not  be  such  as  to  make  length  of  pile  less  than 
that  provided.  The  top  of  the  piling  shall  be  even  and  bound 
together  by  running  a  3  x  8-inch  stringer  along  the  outside  and 
inside  surfaces. 

Each  pile  shall  be  bound  to  this  stringer  by  a  j4 -inch  bolt 
which  shall  be  furnished  with  large  washers  and  a  suitable  nut. 
The  opening  for  the  sluice  boxes  shall  be  made  closely  to  fit  the 
box.  The  cut  ends  of  the  piling  above  the  box  shall  be  bound 
together  by  3  x  8-inch  stringers  which  shall  extend  one  on  the 
inside  and  one  on  the  outside  from  a  point  2  feet  beyond  one 
edge  of  the  opening  to  a  point  2  feet  beyond  the  opposite  edge 
of  the  opening.  These  stringers  shall  be  set  flush  with  the  cut 
ends  of  the  piling  and  each  pile  which  they  cover  shall  be  bound 
to  them  by  a  y2-mch  bolt  properly  washered  and  fitted  with  a 
nut.  The  cut  ends  of  the  piling  below  the  box  shall  be  bound 
together  in  the  fashion  above  described. 

3.  All  sluice  boxes  shall  be  laid  on  2  extra  rows  of  sheet 
piling  composed  of  3-inch  long-leaf-pine  closely  set  together.  The 
planking  shall  be  10  feet  long  and  driven  in  until  the  top  shall 
be  9  inches  below  mean  low  tide.  The  above  provision  regarding 
injury  due  to  driving  and  its  correction  shall  be  observed  here. 
Each  roAv  of  this  sheet  piling  shall  extend  4  feet  each  side  of  the 
sluice  boxes.  Each  row  shall  be  bound  together  at  the  top  in  a 
fashion  similar  to  that  provided  for  the  dike  facing,  and  the  piling 
at  the  sides  of  the  boxes  shall  extend  up  through  the  stringers 
one  foot  and  the  rectangle  thus  formed  shall  be  made  closely  to 
fit  the  boxes. 

4.  At  the  sluice  boxes  the  inner  side  of  the  dike  shall  be 
protected  by  sheet  piling  wing-walls  made  of  2-inch  long-leaf-pine 
without  serious  blemish,  14  feet  in  length  driven  in  until  the  top 
is  one  foot  below  the  level  of  the  dike.     The  above  provision  re- 


Bulletin  306 


19 


garding  injury  due  to  driving  and  its  correction  shall  be  observed 
here.  They  shall  be  bound  together  at  the  top  in  the  same  fashion 
as  the  dike  facing,  and  shall  extend  6  feet  each  side  of  the  sluice 
boxes. 

5.  The  river  side  of  each  sluice  box  shall  be  furnished  with 
a  7  x  4-foot  gate  made  of  tongued  and  grooved  white  pine.  It 
shall  be  composed  of  two  layers,  the  inside  one  being  made  of 
3-inch  7-foot  long  planking  and  the  outside  one  of  Pinch  4-foot 
long  planking  laid  at  right  angles  to  one  another  and  firmly  spiked 
together.  The  gate  shall  be  hung  in  front  of  the  opening  with  a 
suitable  link  hinge  so  that  it  will  readily  open  with  the  falling 
tide  and  readily  close  with  the  rising  tide. 


Fig.   7- 


-Photograph  of  a  tide  gate  and  sluice. 
Mos.  Exter.  Com.) 


(Photo  by  Union  Co. 


Lighter  sluice  gates  have  been  employed  but  no  larger  or 
heavier  ones.  If  the  capacity  of  more  than  one  was  needed  dupli- 
cates have  been  installed.  This  plan  has  been  followed  because 
gates  larger  than  this  have  elsewhere  proven  difficult  to  keep  in 
working  order. 

Recently  Mr.  Brooks  has  devised  another  type  of  sluiceway 
and  tide  gate,  which  the  writer  has  since  found  to  have  been  antici- 
pated, which  he  believes  to  be  superior  in  many  respects  to  any 
of  the  others.  In  this  case  no  box  is  constructed  but  heavily  tim- 
bered bulkheads  are  built  into  the  stream  until  they  stand  within 
approximately  6  feet  of  each  other.  To  render  their  relation  to 
each  other  constant  they  are  bound  together  by  heavy  cross  timbers. 
At  a  point  half-way  between  the  two  ends,  a  pair  of  heavy  6  x  6-inch 
well  braced  timbers  are  set  down  in  such  a  fashion  as  to  form  the 
support  and  resting  place  for  the  tide  gate.  Of  course,  the  joints 
between  each  of  the  upright  posts  and  the  bulk-head  against  which 
it  stands  and  between  the  lower  cross  timbers  and  the  bottom  are 
made  tight. 

The  tide  gate  is  suspended  from  a  cross  timber  located  well 
above  extreme  high  tide,  and  hangs  against  the  upright  posts.  At 
each  end  the  bulkheads  are  fitted  with  slots  in  which  planking 


20 


New  Jersey  Agricultural  Experiment  Stations 


can  be  dropped  to  form  a  coffer  dam.  The  water  between  the 
two  bulkheads  has  merely  to  be  pumped  out,  when  these  dams  are 
in  place,  to  expose  the  gate  for  repairs  and  the  sluiceway  for 
cleaning.  The  top  of  the  sluiceway  thus  formed  is  left  open.  Mr. 
Brooks  holds  that  the  greater  ease  with  which  this  type  of  gate 
can  be  kept  in  good  working  order  is  sufficient  to  warrant  its 
adoption. 

The  problem  of  preparing  a  proper  dike,  sluice  boxes,  and 
tide  gates  for  draining  a  given  area  is  an  engineering  one.  Suffice 
it  to  say  that  the  trenching,  diking,  sluicing,  and  tidegating  must 


D  E 

Fig-.  8. — Relative  level  of  water  on  the  protected  area  as  compared  with  the 
tide.  A.  Sluice  and  gate  in  Maple  Island  Creek.  B.  Same  just  before  the 
sluice  begins  to  discharge.  C.  Same  showing  medium  tide  level,  see  the  level 
of  Mr.  Walden's  boot  soles.  D.  Same  showing-  extreme  high-tide  level,  see 
level  of  Mr.  Walden's  boot  soles.  E.  Same  showing-  relative  level  of  water 
inside  and  outside  the  dikes  under  extreme  high-tide  conditions,  (1)  shows  Mr. 
Walden  standing  at  water  level  inside  the  dike  and  (2)  shows  the  same  man 
standing  at  the  level  reached  by  the  water  outside  the  dike  under  extreme  high 
tide. 


Bulletin  306  21 

be  so  planned  as  to  keep  out  all  but  the  most  extraordinary  high 
tides  and  to  free  the  surface  from  water  within  5  days  after  a 
heavy  rainfall. 

Salt  marshes  protected  in  this  way,  at  certain  times  of  the 
year  are  subject  to  mosquito  breeding  in  the  drainage  ditches.  If 
the  ditches  are  not  sewage-charged,  opening  the  tidegates  and  al- 
lowing the  tide  water  to  flow  in  usually  brings  a  large  enough 
number  of  killifish  to  eliminate  breeding.  If  the  trenching  is  so 
arranged  that  the  water  it  contains  may  be  flushed  out  without 
escaping  into  the  meadow  over  the  surface  of  the  ditches  it  is 
likely  that  introducing  the  tide  regardless  of  the  presence  of  fish 
will  have  a  beneficial  effect.  If  the  ditches  are  heavily  sewage- 
charged  the  use  of  fish  appears  to  be  out  of  the  question  and  any 
value  that  can  come  from  flushing  must  come  through  the  ac- 
celerated movement  of  the  water.  As  a  matter  of  fact,  the  author 
is  inclined  to  believe  that  elimination  of  breeding  in  the  ditches 
of  diked  areas  when  sewage-charged,  is  a  matter  of  removing  the 
water  by  a  pump  or  a  matter  of  covering  it  with  oil  at  regular 
intervals. 

During  the  summer  of  1916  Mr.  John  Dobbins,  chief  inspector 
of  the  Essex  County  commission  worked  out  a  new  method  for 
preventing  mosquito  breeding  on  an  undiked  salt  marsh.  Mr. 
Dobbins  worked  with  a  piece  of  rather  high-lying  meadow  border- 
ing on  Newark  Bay.  He  introduced  small  tide  gates  into  the  main 
outlet  ditches  without  materially  disturbing  the  10  x  30-inch  ditch- 
ing which  had  already  been  established  on  the  meadow. 

When  the  monthly  high  tides  came  the  water-table  had  been 
so  reduced  that  the  overflow  was  promptly  absorbed  by  the  dry  soil 
and  the  ditches,  and  almost  no  trouble  was  experienced  with  breed- 
ing. 

The  cost  of  this  addition  to  the  usual  drainage  system  depends 
upon  the  size  and  number  of  outlet  streams  that  must  be  gated. 
To  what  extent  the  method  will  apply  to  marshes  differing  in  type 
from  this  one,  can  not  at  this  time  be  said,  but  its  efficiency  in 
this  instance  is  such  as  to  merit  attention  from  all  who  have  large 
areas  of  open  marsh  to  protect  from  mosquito  breeding. 

Pumping 

The  need  for  pumps  in  mosquito  control  first  became  apparent 
in  Hudson  County  where  the  railway  grades  and  roadways  had 
cut  the  marsh  up  into  pockets,  the  satisfactory  outleting  of  which 
was  impracticable  from  the  standpoint  of  cost.  In  the  Kearny 
section  of  the  marsh  an  area  of  this  sort,  which  had  its  outlet 
through  Frank  Creek  into  the  Passaic  River,  had  shrunken  until 
parts  of  the  surface  were  scarcely  above  and  perhaps  in  some  cases 
below  mean  low  tide,  and  had  become  charged  with  sewage  from 
the  creek  which  served  as  a  sewer  for  the  towns  of  Kearny  and 
Harrison.  The  creek  emptied  into  the  Passaic  River  through  an 
8  x  12-foot  concrete  culvert  300  feet  long  running  under  the 
Pennsylvania  Railroad  and  the  Delaware,  Lackawanna  and  Wes- 
tern Railroad  tracks.  Tidal  water  from  the  Passaic  River  was 
prevented  from  entering  the  creek  by  means  of  a  pair  of  large 
sluice  gates.    Except  where  the  trunk  sewers  entered,  the  banks  of 


99 


New  Jersey  Agricultural  Experiment  Stations 


Frank  Creek  were  built  up,  but  every  heavy  rainstorm  served  to 
send  it  over  them  and  to  keep  the  adjacent  marsh  soaked  with 
sewage.  By  cleaning  the  creek,  enough  flow  of  water  was  obtained 
to  keep  the  surface  fairly  free  from  breeding  during  ordinary 
dry  seasons,  but  when  heavy  rainfall  came  the  arrangements  were 
shown  to  be  wholly  inadequate  and  large  broods  of  mosquitoes  de- 
veloped. 

It  having  thus  become  evident  that  some  other  step  must  be 
taken,  the  Hudson  County  commission  decided  to  install  a  pump. 
A  12-inch  low-head  centrifugal  electrically-driven  pump  was  placed 
on  the  east  bank  of  the  creek  at  the  lower  end  of  this  area,  at  a 
total  cost  of  about  $1300,  and  all  the  territory  hying  east  of  the 
creek  amounting:  to  about  700  acres  was  ditched  to  it. 


Fig.   9. — Diagram  of  Frank  Creek  area,  showing  ditching  outlets  and 
pumps. 

It  was  quickly  found  that  the  pump  could  handle  the  water 
far  more  rapidly  than  the  trenching  could  bring  it,  and  in  conse- 
quence of  no  considerable  enlargement  of  the  trenching  scheme,  the 
pump  has  not  worked  at  full  capacity  except  for  brief  periods. 
The  maintenance  and  operation  charge  during  the  1915  mosquito 
season  averaged  about  $80  a  month.  In  spite  of  the  fact  that  the 
200  acres  lying  west  of  the  creek  had  to  depend  upon  the  sluggish 
over-filled  creek  for  drainage  and  that  the  trenching  on  the  eastern 
side  was  not  adequate  to  bring  the  water   down  with  sufficient 


Bulletin  306 


23 


rapidity  to  permit  prompt  removal  of  surface  water,  and  that  the 
banks  of  the  creek  were  not  sufficiently  built  up  to  prevent  the 
occasional  spilling-  of  sewage  water  over  them,  the  area  was  freer 
from  mosquitoes  in  1915  than  it  had  been  either  of  the  two  seasons 
previous,  although  the  season  was  as  bad  as  or  worse  than  either 
of  the  others.  When  more  trenching  has  been  cut  to  lead  the 
water  to  the  pump,  when  the  200  acres  lying  west  of  the  creek 
are  drained  to  the  pump,  and  when  the  banks  of  the  creek  are 
built  up  so  that  the  water  cannot  spill  over,  all  breeding  of  mos- 
quitoes should  be  eliminated  from  the  areas  served  by  the  pump. 


C 


D 


Fig.  10. — Twelve-inch  centrifugal  pump,  which  was  installed  to  drain 
an  area  of  marsh  slightly  below  sea  level.  (Photos  by  Hud- 
son. Mos.  Exter.  Com.) 

A  smaller  area,  amounting  to  about  150  acres  lying  just  south 
of  the  one  previously  discussed  and  depending  upon  Frank  Creek 
for  its  outlet,  was  served  in  1915  by  a  high-head  4-inch  centrifugal 
gasoline-driven  pump  that  cost  about  $600  to  install.  It  was  op- 
erated and  maintained  in  such  a  manner  as  to  prevent  serious 
breeding  of  mosquitoes  in  that  area.  This  area  is  not  sewage- 
charged  and  depends  for  its  supply  of  water  upon  rainfall  and 
possibly  a  small  amount  of  seepage  from  the  Passaic  River. 

Whether  an  area  shall  be  pumped,  what  type  and  what  ca- 
pacity of  pump  shall  be  employed,  what  trenching  must  be  used  to 
bring  the  water  to  the  pump  and  to  take  it  away,  are  engineering 
questions  and  persons  having  to  answer  them  will  do  well  to 
secure  the  advice  of  a  competent  engineer. 


24  New  Jersey  Agricultural  Experiment  Stations 

Larvicides 

The  work  on  this  subject  thus  far  has  seemed  to  indicate  fuel 
oil  as  the  best  larvicide  for  general  use.  Fuel  oil  is  a  variable 
product  and  the  question  as  to  what  grade  is  best  naturally  arises. 
The  grades  range  from  a  light  straw  yellow  to  almost  or  quite 
black.  The  former  disappears  too  rapidly  and  the  latter  forms  a 
film  with  too  great  difficulty.  The  best  results  apparently  follow 
the  use  of  an  oil  that  is  light  in  color  but  which  betrays  con- 
considerable  viscosity.  It  is  possible  to  obtain  oils  having  these 
characters.  The  author  has  been  furnished  with  such  types  by  the 
Standard  Oil  Company.  In  summing  the  matter  up,  we  may  say 
that  any  oil  which  flows  readily,  is  cheap,  and  does  not  disappear 
too  quickly  will  be  fairly  satisfactory.  The  method  of  application 
depends  on  the  viscosity  of  the  oil  and  the  size  of  the  pool  treated. 
A  very  viscous  oil  should  be  delivered  as  a  mist  by  a  sprayer, 
but  light  oils  may  be  satisfactorily  applied  with  a  common  garden 
sprinkling  pot  if  the  pool  is  small,  or  as  a  slender  so! id  jet  under 
pressure  if  the  pool  is  large. 

Under  conditions  where  immediate  killing  of  the  larva1  is  es- 
sential, a  substance  such  as  the  larvicide  made  >and  used  by  the 
Isthmian  Canal  Commission  seems  best.  Both  these  substances, 
however,  have  certain  glaring  defects  which  render  them  anything 
but  ideal  larvicides.  Both  substances  destroy  plant  growth  and 
make  treated  pool  unsightly,  and  both  disappear  in  a  short  time. 

The  really  satisfactory  larvicide  should  be  cheap  in  cost,  reas- 
onable in  the  expense  of  application  and  should  remain  effective 
in  the  pool  for  a  season,  reappearing  as  often  as  the  pool  refills 
with  water.  It  should  not  be  deadly  to  plants  and  not  seriously 
injurious  to  the  higher  animals  and  man.  Perhaps  the  ideal  larvi- 
cide as  thus  defined  will  not  be  found,  but  room  for  improvement 
on  what  we  already  have  is  so  great  that  a  serious  study  of  the 
problem  has  seemed  worth  while.  The  report  which  follows  rep- 
resents the  barest  beginnings. 

Sulfuric  Acid 

Because  of  its  toxic  nature,  its  cheapness  and  its  availability, 
sulfuric  acid  was  selected  for  testing.  A  series  of  experiments 
served  to  show  that  under  laboratory  conditions  fully  grown  lar- 
vae of  Culex  pipiens  Linn,  perished  in  2  days,  in  a  mixture  of  1 
volume  of  sulfuric  acid  testing  1.84  sp.  gr.  to  2000  volumes  of 
distilled  water.  Another  series  served  to  show  that  1  volume  of 
acid  to  1000  volumes  of  water  testing  nearly  3  per  cent  salinity 
(concentrated  sea  water  having  been  added  to  the  distilled  water) 
destroyed  larva?  of  A.  cantator  from  1/8  inch  long  up  to  maturity 
in  2  days'  time.  Still  another  series  of  laboratory  experiments 
served  to  show  that  1  volume  of  acid  added  to  1000  volumes  of 
sea  water  showing  10  per  cent  salinity  destroyed  in  4  days  the 
larvai  (ranging  from  1/8  inch  long  up  to  maturity)  of  Aedes  soUici- 
laiis  AVlk.  Obviously  sulfuric  acid  was  effective  at  dilutions  suf- 
ficiently high  to  render  its  use  practicable  from  the  standpoint  of 
cost. ' 

The  next  step  was  to  determine  whether  it  disappeared  from 
treated  pools,  and  at  what  rate.  For  the  preliminary  study  of  this 
phase  of  the  problem  a  small  pool  8  feet  wide  by  12  feet  long  was 


Bulletin  306  25 

selected.  The  bottom  and  sides  were  of  red  shale  soil  and  a  con- 
siderable amount  of  old  troughs  and  leaders  had  been  thrown 
into  it.  Samples  taken  immediately  after  treatment  showed  9.31 
parts  per  10,000  parts  of  water.  Samples  taken  1  days  later  show- 
ed 2.15  parts  per  10,000.  Samples  taken  18  hours  later  showed 
2.00  parts  per  10,000.  Samples  taken  2  days  later  showed  1.96 
parts  per  10,000.  At  this  time  evaporation  had  greatly  lowered 
the  level  of  the  pool.  Samples  taken  1  day  later  following  a  small 
rain  showed  1.47  parts  per  10,000.  Samples  taken  17  days  later 
showed  0.16  parts  per  10.000. 

In  3  weeks,  with  never  enough  rain  to  fill  the  pool  to  over- 
flowing, starting  with  it  brimful,  the  acidity  dropped  from  9.31 
parts  per  10.000  to  0.16  parts  per  10,000.  Thus  it  appears  that  the 
acid  as  an  efficient  treatment  lasted  no  longer  than  fuel  oil. 

Not  being  satisfied  with  our  ability  to  prevent  ail  artificial 
variations,  such  as  those  occasioned  by  throwing  pieces  of  sheet 
iron  or  tin  cans  into  the  pool,  four  wooden  wash  tubs  were  secured 
for  a  further  test.  One  was  filled  three-quarters  of  the  way  to  the 
top  with  red  shale  soil,  another  one-half  way  to  the  top,  another 
one-quarter  the  way  to  the  top,  and  another  given  no  soil  what- 
ever. The  tubs  were  placed  in  the  yard  just  back  of  the  Entom- 
ology Building.  It  was  planned  to  acidulate  distilled  water  at  the 
rate  of  1  part  of  acid  to  1,000  parts  of  water  and  to  fill  all  tubs. 
Through  a  misunderstanding  an  assistant  filled  the  tubs  with  wat- 
er, estimated  the  volume,  and  acidulated  on  that  basis  at  the  rate 
of  1  volume  of  the  acid  to  1,000  volumes  of  water.  The  experiment 
was  set  on  September  18  and  followed  until  October  15.  On  Sep- 
tember 19  samples  from  the  tub  with  most  soil  showed  1.6  volumes 
to  1,000  volumes.  Samples  from  tub  half -filled  with  soil  showed 
1.6  volumes  to  1,000  volumes.  Samples  from  tub  one-fourth  filled 
showed  1.3  volumes  to  1,000  volumes.  Samples  from  tub  without 
soil  showed  1.3  volumes  to  1,000  volumes. 

Samples  taken  October  15  showed  for  the  first  tub,  0.011  vol- 
umes to  1,000  volumes,  the  second  0.45  volumes  to  1,000,  the  third 
0.52  volumes  to  1,000  and  the  fourth  1.2  volumes  per  1,000 
volumes. 

The  tub  experiment  is  thus  seen  to  confirm  the  results  obtained 
at  the  pool  in  that  it  shows  a  strong  diminution  of  the  acid  when 
in  contact  with  soils.  The  detailed  data  shows  that  the  fall  in 
acidity  was  steady — much  steadier  than  that  in  the  pool. 

Inasmuch  as  practically  all  pools  are  in  soil  or  other  sub- 
stance which  may  combine  with  sulfuric  acid  and  in  many  cases 
contain  objects  which  the  acid  may  attack,  it  seems  unlikely  that 
sulfuric  acid  can  have  any  great  importance  as  a  larvicide. 

Chlorine 

A  preliminary  investigation  of  this  substance  as  found  in 
bleaching  powder  was  undertaken  principally  because  of  its  cheap- 
ness. Dr.  Smith  had  already  shown  that  it  could  be  used  as  a 
larvicide  of  limited  application.  By  a  series  of  laboratory  tests 
it  was  quickly  found  that  0.5  gm.  of  the  commercial  bleaching 
powder  to  1000  c.  c.  of  water  would  destroy  all  stages  of  C.  pipiens 
larvae.  A  study  of  its  persistance  was  then  undertaken.  To  jars 
of  distilled  water  on  September  23  commercial  bleaching  powder 
was  added  as  follows :     Jar  No.  1,  1  to  100 ;  Jar  No.  2,  1  to  1000 ; 


26  New  Jersey  Agricultural  Experiment  Stations 

Jar  No.  3,  1  to  10,000.  Samples  taken  September  23  showed  for 
No.  1,  73.6  parts  of  chlorine  per  100.000 ;  No.  2,  6.6  parts  per 
100,000,  and  No.  3,  0.6  parts  per  100,000.  Samples  taken  October 
1  showed  for  No.  1,  67.8  parts ;  No. '  2,  6.0  parts  and  No.  3,  0.0 
parts.  The  reduction  continued  steadily  until  October  13  when 
the  readings  were  discontinued.  At  this  time  No.  1  showed  30.1 
parts  per  100,000  and  No.  2,  2.0  parts  per  100,000. 

All  things  considered  the  chlorine  showed  remarkable  per- 
sistence but,  of  course,  was  constantly  disappearing.  "When  in 
addition  to  its  habit  of  disappearing  from  distilled  water  in  glass 
vessels,  Ave  consider  its  habit  of  attacking  just  such  substance  as 
would  be  found  in  pools,  it  does  not  seem  likely  that  chlorine  can 
have  more  than  a  limited  use  as  a  mosquito  larvicide. 

Electrolysis 

Early  in  the  season  the  American  Electricide  Company  of 
Washington,  D.  C,  approached  the  Experiment  Station  with  a 
proposition  to  destroy  mosquito  breeding  and  render  the  marsh 
uninhabitable  for  the  mosquito  by  the  passage  of  an  electric  cur- 
rent. This  company  was  invited  to  make  a  demonstration  at  its 
own  cost. 

On  Saturday,  July  31,  1915,  the  machinery  consisting  of  a 
gasoline-engine-driven  dynamo,  connecting  wires,  and  electrodes 
was  set  up  on  the  Linden  Meadow  near  Grasselli,  New  Jersey,  and 
a  demonstration  run  made.  Pools  well  stocked  with  nearly  mature 
wrigglers  of  A.  sollicitans  were  in  easy  reach.  A  line  of  several 
carbon  electrodes  was  run  along  one  edge  of  one  of  these  pools  and 
a  line  of  metal  electrodes  along  the  opposite  side,  the  two  lines 
running  parallel  to  each  other  and  about  15  feet  apart.  For  fully 
one  hour  the  current  was  passed.  The  results  are  transcribed  di- 
rectly from  the  Entomologist's  notes.  "At  5.15  p.  m.,  I  examined 
the  pool  and  found  an  abundance  of  living  larvae  and  pupae  but 
no  dead  ones  whatever.  At  this  time  the  grass  was  full  of  freshly 
emerged  adidts  none  of  which  seemed  to  be  in  any  way  incon- 
venienced by  the  treatment.  On  the  afternoon  of  August  1  just 
21  hours  and  40  minutes  after  the  electrolytic  treatment  ceased,  I 
examined  the  treated  pool  and  found  the  conditions  as  they  were 
the  previous  day  except  that  the  number  of  larvae  had  slightly 
decreased  and  the  number  of  pupae  increased,  as  had  the  adults. 
On  the  morning  of  August  2  the  pool  was  re-examined  by  a  rep- 
resentative of  Mr.  E.  W.  Gies,  chief  inspector  of  the  Union  County 
Mosquito  Extermination  Commission,  and  no  evidence  whatever  of 
killing  found." 

A  report  of  our  finding  Avas  promptly  rendered  to  the  com- 
pany. representatiAres  of  Avhich  then  expressed  the  intention  of 
keeping  the  machine  on  the  marshes  and  AA'orking  the  problem  out. 

Nitre  Cake 

This  is  a  by-product  of  gun-cotton  making  and  furnished  to 
us  by  the  Du  Pont  PoAA^der  Company.  The  saturated  solution  is 
weakly  acid,  requiring  1.59  c.c.  of  N/50  sodium  hydroxide  to 
neutralize  5  c.  c.  The  larval  tests  AAdth  various  strengths  of  this 
substance  in  distilled  Avater  indicated  that  nothing  AA'eaker  than  1  to 
100  could  be  depended  on  to  kill,  but  the  numbers  used  weie  too 
small.     The  pupa?  survived  in  a  saturated  solution. 


Date  Due 

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1 '-'  t : ; 

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